Sealing devices have been conventionally used, each configured to seal an annular gap between a housing having a shaft hole and a shaft inserted through the shaft hole in a manner to conduct a movement relative to the housing, such as in case of a piston seal, rod seal, or the like, where each sealing device comprises a combined seal including: a slide ring acting as a sliding member to be abutted on a sliding surface of a mating member; and a back ring combined with the slide ring and joined to that surface (outer peripheral surface or inner peripheral surface) of the slide ring which surface is reverse to the sliding surface of the slide ring, in a manner to provide the slide ring with a predetermined resilient force (Patent Documents 1 and 2).
Such a sealing device is fitted in an annular concave groove provided to face the annular gap, such that the slide ring side is contacted with a sliding surface of the mating member.
It is difficult to fit such a slide ring into the annular concave groove, particularly when a high strength material is used for the slide ring. As such, it has been practiced to provide the slide ring with a through-cut in a direction traversing the circumferential direction of the slide ring, in a manner to cause the slide ring to be expanded at the through-cut, thereby improving an attaching ability of the slide ring.
FIG. 6 is a cross-sectional view of such a sealing device. This sealing device 100 comprises a slide ring 200, and a back ring 300 joined to an inner peripheral surface side of the slide ring, thereby constituting a combined seal.
The sealing device has a through-cut 201 in a step cut shape comprising: a single circumferential cut 201A extending over a predetermined length along a circumferential direction of the slide ring 200; and two axial cuts 201B, 201B extending from both ends of this circumferential cut 201A in mutually opposite directions, respectively, along the axial direction (X direction in this figure) of the slide ring 200; in consideration of sealability.
Such a slide ring 200 is fabricated at a lower cost, by typically adopting a mold formed with a cavity corresponding to a slide ring shape, in a manner to inject a resin material into the mold.
FIG. 7 is a cross-sectional view of a conventional mold to be used upon injection molding the slide ring 200.
The mold 400 has a cavity 401 therein corresponding to the slide ring shape. The mold 400 is typically formed with junction of molds 402A, 402B along a circumferential direction of the mold at positions corresponding to both of outer peripheral side and inner peripheral side of a substantially middle region of the slide ring 200 in its axial direction after molding, respectively, so as to facilitate drawing of the molded slide ring 200 from the mold, and the mold 400 is made to be dividable into two partial molds 400A, 400B at the junction of molds 402A, 402B, thereby allowing the mold to be opened in the axial direction of the slide ring 200.